JSFiddle - React, Tailwind, and code Playground

HTML

<form action="url.php" id="id1" method="post">
    <label>
        <input type="radio" name="choixDest" value="url1.php" checked />URL 1</label>
    <label>
        <input type="radio" name="choixDest" value="url2.php" />
</form>URL 2</label>
<p>L'url de destination : <span></span>

</p>

JavaScript

// En utilisant du jQuery:
    $(document).ready(function () {
        $(':radio[name="choixDest"]').click(function () {
            console.log($(this).val());
            $('form#id1').attr('action', $(this).val());
            $('p > span').text($('form').attr('action'));
        });
    });